整理了postgresql的系统表关联的常用SQL，如下：

--查看数据库  select * from pg_database;    --查看表空间  select * from pg_tablespace;    --查看语言  select * from pg_language;    --查看角色用户  select * from pg_user;  select * from pg_shadow;  select * from pg_roles;    --查看会话进程  select * from pg_stat_activity;    --查看表  SELECT * FROM pg_tables where schemaname = 'public';    --查看表字段  select * from information_schema.columns where table_schema = 'public' and table_name = 'pf_vip_org';    --查看视图  select * from pg_views where schemaname = 'public';  select * from information_schema.views where table_schema = 'public';    --查看触发器  select * from information_schema.triggers;    --查看序列  select * from information_schema.sequences where sequence_schema = 'public';     --查看约束  select * from pg_constraint where contype = 'p'    --u unique,p primary,f foreign,c check,t trigger,x exclusion    select a.relname as table_name,b.conname as constraint_name,b.contype as constraint_type from pg_class a,pg_constraint b where a.oid = b.conrelid and a.relname = 'cc';    --查看索引  select * from pg_index ;    --查看表上存在哪些索引以及大小  select relname,n.amname as index_type from pg_class m,pg_am n where m.relam = n.oid and m.oid in (  select b.indexrelid from pg_class a,pg_index b where a.oid = b.indrelid and a.relname = 'cc');    SELECT c.relname,c2.relname, c2.relpages*8 as size_kb  FROM pg_class c, pg_class c2, pg_index i  WHERE c.relname = 'cc' AND  c.oid = i.indrelid AND  c2.oid = i.indexrelid  ORDER BY c2.relname;     --查看索引定义  select b.indexrelid from pg_class a,pg_index b where a.oid = b.indrelid and a.relname = 'cc';  select pg_get_indexdef(b.indexrelid);    --查看过程函数定义  select oid,* from pg_proc where proname = 'insert_platform_action_exist'; --oid = 24610  select * from pg_get_functiondef(24610);    --查看表大小(不含索引等信息)  select pg_relation_size('cc');                         --368640 byte  select pg_size_pretty(pg_relation_size('cc'))   --360 kB    --查看DB大小  select pg_size_pretty(pg_database_size('smiletao'));   --12M    --查看服务器DB运行状态  [postgres@eyar ~]$ pg_ctl status -D $PGDATA  pg_ctl: server is running (PID: 2373)  /home/postgres/bin/postgres "-D" "/database/pgdata"     --查看每个DB的使用情况(读,写,缓存,更新,事务等)  select * from pg_stat_database    --查看索引的使用情况  select * from pg_stat_user_indexes;    --查看表所对应的数据文件路径与大小  SELECT pg_relation_filepath(oid), relpages FROM pg_class WHERE relname = 'empsalary';    --查看索引与相关字段及大小   SELECT n.nspname AS schema_name,          r.rolname as table_owner,         bc.relname AS table_name,         ic.relname AS index_name,         a.attname  AS column_name,         bc.relpages*8 as index_size_kb         FROM pg_namespace n,         pg_class bc,             -- base class         pg_class ic,             -- index class         pg_index i,         pg_attribute a,           -- att in base         pg_roles r    WHERE bc.relnamespace = n.oid       and i.indrelid = bc.oid       and i.indexrelid = ic.oid       and bc.relowner = r.oid       and i.indkey[0] = a.attnum       and i.indnatts = 1       and a.attrelid = bc.oid       and n.nspname = 'public'       and bc.relname = 'cc'    ORDER BY schema_name, table_name, index_name, attname;    --查看PG锁  select * from pg_locks;    备注：relpages*8 是实际所占磁盘大小    --查看表空间大小  select pg_tablespace_size('pg_default');    --查看序列与表的对应关系    WITH fq_objects AS (SELECT c.oid,c.relname AS fqname ,                             c.relkind, c.relname AS relation                      FROM pg_class c JOIN pg_namespace n ON n.oid = c.relnamespace ),         sequences AS (SELECT oid,fqname FROM fq_objects WHERE relkind = 'S'),        tables    AS (SELECT oid, fqname FROM fq_objects WHERE relkind = 'r' )            SELECT         s.fqname AS sequence,         '->' as depends,         t.fqname AS table        FROM         pg_depend d JOIN sequences s ON s.oid = d.objid                    JOIN tables t ON t.oid = d.refobjid             WHERE         d.deptype = 'a' and t.fqname = 'cc';